The latest U.S. Census estimates show that international immigration accounted for much of the growth in New Castle County, with domestic migration accounting for population gains in faster-growing Sussex County.
According to Census Bureau estimates, Delaware’s population rose from 897,894 in 2010 to 967,161 in 2018. Sussex County’s population rose by about 15 percent during that period, with Kent County up about nine percent and New Castle County rose by four percent.
New Castle County saw a decrease of 7,200 in-migration from other states, compared to a gain of more than 31,400 in Sussex County. The number of deaths in Sussex outstripped the number of births by about 800 and suggests a growing population of retirees.
Much of the increase in New Castle County’s growth in population came from international immigration, which posted a gain of more than 11,000, compared to 1,200 in Sussex County and 2,200 in Kent County.
Net migration includes the international migration of both native and foreign-born populations. The numbers include the Armed Forces and migration to and from Puerto Rico.
Population growth in New Castle County remained low, due in part to legacy employers, such as DuPont and AstraZeneca. All made big job cuts from 2010 to 2018. The county lost both of is auto plants shortly before 2010.
At the same time, employment at financial services companies remained relatively steady or increased modestly during the eight-year time frame. Health care employment increased in all three counties. Hospitality and construction employment have also shown gains in recent years in Delaware.